An air micrometer is available as one of measuring apparatuses for measuring the shape of a hole. For the conventional air micrometer, a measuring head is inserted into a hole, and compressed air is injected from a nozzle of the measuring head toward the wall surface of hole, by which the back pressure of nozzle is detected. Since the back pressure of nozzle depends on a gap between the inside wall of hole and the nozzle, the detected value can be converted into the inside diameter of the hole by comparing the value with the master reference value having been determined in advance. The conventional air micrometer can determine the shape of a hole by continuously measuring the inside diameter while the measuring head is moved in and out with respect to the hole.
However, for the conventional air micrometer, since the measuring head cannot be moved into or out of a bent or curved hole, the shape of a bent or curved hole cannot be measured.
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide hole shape measuring method and apparatus capable of measuring the shape of various holes.